Function is_builtin_type 

pub fn is_builtin_type(name: &str) -> bool

Type names a program may write as a namespace, such as Vector.of.

This is cove_schema::builtins::is_builtin_type, re-exported so that the interpreter still asks one module about builtins. Whether name is a builtin type a program may write as a namespace, as in Vector.of(...).